107 hemodialysis patients at high risk for intradialytic bleeding due to previous surgery or active bleeding from other sites were treated with nafamostat mesilate (FUT-175; FUT) as hemodialysis anticoagulant for 2 weeks. In contrast to heparin. FUT prolonged clotting times only in the extracorporeal circuit. Clotting times were not prolonged even at the conclusion of the treatment, and bleeding from the puncture site after removal of the needle was shorter than with heparin. The exacerbation of bleeding by hemodialysis was noted in only 21 out of 573 hemodialysis procedures (3.7%), and 134 of 145 hemodialysis procedures (92.4%) with active bleeding were successfully completed without increasing the bleeding. Adverse effects of FUT were noted in only 6 cases (5.6%) or 1.2% of HD procedures. These results indicate that FUT is a very useful anticoagulant for HD, especially in patients with high risk of bleeding.